Method of treating piston rings



- Aug. 2, 1938. GJDEE 7 2,125,606

METHOD OF TREATING PISTON RINGS Filed Jan. 23, 1936 INVENTOR. I

Qu t J D685,

ATTORNEYJ Patented Aug. 2, 1938 UNITED. STATES PATENT OFFICE.

1 3 Claims. My invention 'relates, to improvements in method of treatingpiston rings, preferably those formed of steel or steel alloys in orderto insure longer wearing qualities on that part of the ring coming incontact with the cylinder walls of an explosive engine. v r

I have found that steel rings, if properly heattreated, and if properlycase hardened on their outer periphery, or wearing surface, have decidedadvantages, from the wearing standpoint and eificiency of performanceand from other standpoints, over the ordinary commercial type of castiron rings.

I have found that rings which had had their outer periphery nitridedhave particularly fine wearing qualities. I have also found that ringsformed of nitralloy, when nitrided on their outer periphery, aredecidedly advantageous in use over other types of rings.

It is one of the objects of my invention to provide a method formaintaining the piston rings in position and for preventing warping ofthe rings during the heat-treatment necessary in the nitriding manner oftreating, and to insure the proper treatment of thesurfaces of the ring.I have found from experience that if the entire ring is nitrided tothesame extent as the outer periphery, the ring will be so brittle that itwill tend to break and will not stand up under wear. I have found,however, that if the outer periphery of the ring is nitridedto a greaterextent than the rest of the ring, this brittleness is reduced tosuch anextent that there is no danger of the ring breaking and at the same timethe wearing surface of the ring is materially hardened.

For the purpose of disclosing my invention, I have illustrated aparticular type of supporting member for holding the rings during thenitriding process. In the drawin Fig. 1 is a side elevation of the coremember, on which the rings are mounted;

Fig. 2 is a longitudinal sectional view thereof;

Fig. 3 is a transverse sectional view thereoff and Fig. 4 is anelevation, looking in another direc-' tion, of the core.

In carrying out my invention, the rings, aftercylindrical cast iron coreI provided at its bottom with an annuar flange 2 on which is adapted torest a bottom ring supporting member 3. This bottom ring supportingmember 3 may be formed integrally with the flange or may be a separatering supporting member and allowed to rest on the flange. .Extending ina line parallel with the axis of the core and formed on the outerperiphery of the core, is a rib 5 which projects beyond the peripheralsurface of the core and pro-- vides on either side an abutment orshoulder.

That-portion of the core extending on the periphery thereof to abouthalf way around fromthe rib 5 is provided with a plurality of flattenedsurfaces 6 which provide, in effect, aseries of flat surfaces extendingparallel to the axis of the core and arranged on the periphery of thecore about half way around. In addition to the core, I provide aremovable ring l which has suflicient inner diameter to slide up anddown on the'core,

and extending through the side wall of the core,

a pair of clamping openings 8 and El adapted to receive a driving wedgeit, which wedge, when inserted in position and contacting the top of thering i, will tend to move the ring downwardly on the core. I

After the rings have been formed by suitable mechanism, they areassembled on thecore, one on top of the other, the bottom piston ringresting upon the bottom ring 3 of the core with the gapped ends of eachpiston ring abutting against the shoulders formed by the rib ii. Thediameter of the core is such that when the rings areassembledthereonthey are in substantialcontact at all points around the true portion ofthe core,

that is, the unfiattened surface portion of the core, and contact thecore around that portion having the flat surfaces 6 with the edges ofthese flattened surfaces only. The rings are assembled one on top of theother until they are high enough on the core to permit,, when the topring l is placed in position and the wedge l0 driven'in, considerablepressure to be exerted on the rings to compress them together. 1

After the rings have been tightly compressed on the core, the coremember, with its assembled rings, is then subjected to the nitridingprocess.

This process briefly consists of a process by.

which extraordinary hardness is developed on the part subjected to theprocess by subjecting the parts for a suflicient period of time to anammonia gas under temperature. a

More particularly, it consists in subjecting the parts made of asuitable alloy steel to the ammonia gas treatment; v

In carrying out this process, the parts are usually introduced into afurnace in which the temperature can be closely controlled preferablyata temperature of between 950 and 9'75 degrees F. Although at times thetemperatures have been known to run up ashigh as 1,200 degrees F. Theparts to be nitrided are placed in a container which is gas-tight andwhich, however, has suitable connections with the ammonia system. Thisgas-tight container is placed in the heating chamber of the furnace andthe furnace sealed and during the heating process ammonia gas is causedto flow through the container in which the parts to be treated areplaced. After sufiicient time has elapsed to obtain the desired 4casedepth the furnace is allowed to cool and a light flow of gascontinued through the container until the work has reached a fairly lowtemperature.

By the above-described method of assembling the piston rings to benitrided on the above-described core, and maintaining a sufllcientpressure upon the rings to compress them to the proper degree, I amenabled to nitride the rings in order to case harden the outerperiphery'to a greater extent and to subject the rings to the nitridingprocess and the heat required therefor without the rings being distortedin any direction so that, after the rings have been nitrided, furthertreatment of the'same to true them in any direction is unnecessary.

v Furthermore, by this method of nitriding the rings I am enabled toobtain a perfectly true ring without distortions, having an extremelyhard wearing surface and at the same time maintain the proper resiliencyin the metal of the ring to insure the expansion of the ring againstthe-walls of the cylinder of the explosive engine to insure gas-tightfit between the ring and the walls of the engine at all times.

I claim as my invention:

1. The method of treating piston rings fabricated from steel whichconsists in assembling a series of rings in a stack in axial alignmentcompressing said stack, masking at least a. portion of the innercircumference of the rings and supporting said rings against inwardcircumferential distortion and then subjecting the assembled stack,while under axial pressure, to nitriding treatment to harden the outerperiphery of the ring.

2. The method of treating piston rings fabricated from steel whichconsists in assembling a series of rings in a stack in axial alignment,compressing said stack, supporting the rings against inwardcircumferential distortion con-' tinuously' throughout a portion oftheir inner circumference and at spaced intervals throughout theremaining portion of their circumference,

masking at least a portion of the inner circumference of said rings andthen subjecting the rings, while under pressure, to nitriding treatmentto harden the outer periphery;

3.- The method of treating piston rings fabricated from steel and havinga gap between their ends which consists in assembling a series of ringsin axial alignment, maintaining the ends of their rings in their spacedrelation, compressing said stack of rings, supporting said rings againstinward distortion continuously throughout a portion of their innerperiphery and at spaced intervals throughout that portion adjacent theends of the rings and subjecting said stack, while under pressure, tonitriding treatment to harden the outer peripheries of the rings.

' GEORGE J DEEB.

